Property
evflagWhen a symbol x has the evflag property,
the expressions ev(expr, x) and expr, x
(at the interactive prompt) are equivalent to ev(expr, x = true).
That is, x is bound to true while expr is evaluated.
The expression declare(x, evflag)
gives the evflag property to the variable x.
The flags which have the evflag property by default are the following:
algebraic,
cauchysum,
demoivre,
dotscrules,
%emode,
%enumer,
exponentialize,
exptisolate,
factorflag,
float,
halfangles,
infeval,
isolate_wrt_times,
keepfloat,
letrat,
listarith,
logabs,
logarc,
logexpand,
lognegint,
lognumer,
m1pbranch,
numer_pbranch,
programmode,
radexpand,
ratalgdenom,
ratfac,
ratmx,
ratsimpexpons,
simp,
simpsum,
sumexpand, and
trigexpand.
Examples:
(%i1) sin (1/2); 1 (%o1) sin(-) 2 (%i2) sin (1/2), float; (%o2) 0.479425538604203 (%i3) sin (1/2), float=true; (%o3) 0.479425538604203 (%i4) simp : false; (%o4) false (%i5) 1 + 1; (%o5) 1 + 1 (%i6) 1 + 1, simp; (%o6) 2 (%i7) simp : true; (%o7) true (%i8) sum (1/k^2, k, 1, inf); inf ==== \ 1 (%o8) > -- / 2 ==== k k = 1 (%i9) sum (1/k^2, k, 1, inf), simpsum; 2 %pi (%o9) ---- 6 (%i10) declare (aa, evflag); (%o10) done (%i11) if aa = true then YES else NO; (%o11) NO (%i12) if aa = true then YES else NO, aa; (%o12) YES